1. Field of the Invention
The present invention relates to a semiconductor device and method of manufacture thereof, a circuit board, and an electronic instrument.
2. Description of Related Art
With the recent increasingly compact nature of electronic instruments, there is a demand for semiconductor device packages appropriate for high-density mounting. In response to this, surface-mounted packages have been developed, such as Ball Grid Array (BGA) and Chip Scale/Size Package (CSP). With such surface-mounted packages, a substrate is often used on which a wiring pattern for connection to the semiconductor chip is formed. Penetrating holes are formed in substrate, and external electrodes are often formed so as to project through these penetrating holes from the surface opposite to that of the wiring pattern.
With a semiconductor device to which a package of this construction is applied, after mounting on the circuit board, because of the difference in coefficient of thermal expansion between the circuit board and semiconductor device, a stress may be applied to the external electrodes, and cracks may form in the external electrodes.